Hydraulic lift truck with small number of fluid lines

ABSTRACT

A lift truck of the type including a vehicle component having a mast, and a clamp on the mast having clamp arms for gripping a load and moving it laterally as well as lifting it, including as few as three fluid lines to the clamp, for individually moving the arms laterally in clamping and releasing directions, and shifting both together laterally in each direction, and three manually operable control valves for effecting those movements.

United States Patent Lake Y HYDRAULIC LIFT TRUCK WITH SMALL NUMBER OFFLUID LINES Edward 'E; Lake, Battle Creek, Mich.

Assignee: Clark Equipment Company Filed: Dec. 28, 1970 Appl. No.:101,547

Inventor:

us. Cl ..214/6s3 Int. Cl. ..B66f 9/18 Field of Search ..2l4/653References Cited I UNITED STATES PATENTS 3,184,088 5/1965 Berge..2l4/653 51 Sept. 19, 1972 Primary Examiner-Gerald M. ForlenzaAssistant ExaminerGeorge F. Abraham Attorney-Paul H. Gallagher ABSTRACTA lift truck of the type including a vehicle component having a mast,and a clamp on the mast having clamp arms for gripping a load and movingit laterally as well as lifting it, including as few as three fluidlines to the clamp, for individually moving the arms laterally inclamping and releasing directions, and shifting both together laterallyin each direction, and three manually operable control valves foreffecting those movements.

7 Claims, 10 Drawing Figures PATENTEDsEP 1 e um 3.692.198

saw 1 or 4 EDWARD E. LAKE ATTORNEY PATENTEB 19 I973 3.692.198

SHEET 2 BF 4 I o -Z a N g FIG. 2

INVENTOR EDWARD E. LAKE A IORNEY PATENTEDSEP 19 m2 3.692.198

SHEET 3 BF 4 FIG. 5

FIG. 6

FIG. 7

INVENTOR EDWARD E. LAKE ATTORNEY PATENTED l 9 i972 3.6 92,198

saw u or 4 FIG. 8

FIG. IO

INVENTOR EDWARD E. LAKE ATTORNEY FIELD OF THE INVENTION v The'inventionlies in the field of hydraulic lift trucks. Such a lift truck as isknown, includes a mast, and a lifting component such as a clamp, fork,etc. The lifting component, as a clamp, has side clamp arms engaging theload in lateral direction, and operative for moving it laterally, and ofcourse lifting it. The clamp, arms preferably aremovable individually,and in order to effectively move them in the necessary direction forhandling the load, it has been necessary heretofore to have a largenumber-of fluid lines, most usually-six. Those lines necessarily go overthe mast in order to accommodate the lifting movements of the clampmeans, and because of the necessity of a relatively large number of suchfluid lines, the difficulties encountered are' great; those difficultiesincrease as the number of lines increase.

OBJECTS OF THE INVENTION A broad object of the invention is to produce ahydraulic lift truck of the type incorporating a vehicle and a liftingcomponent which includes clamping means for clamping the load to belifted or handled, and a mast mounting the lifting component andproviding the means for vertically moving the, lifting component, and inwhich the hydraulic lines leading to the lifting component or clampmeans are necessarily positioned over the mast, and wherein such numberof fluid lines are reduced to a minimum substantially less than has beenpossible heretofore.

A more specific object is to provide alift truck of the characterreferred to in which the fluid lines can be reduced in number from theusual six as has been necessary heretofore, to four, for example, andeven three. I

Still another object is to provide a hydraulic lift truck of thecharacter referred to above which includes a novel valve arrangement andcontrol thereof whereby to enable full and effective operation of theclamp means through the relatively few hydraulic lines as referred to,such as four, or three.

DESCRIPTION OF A PREFERRED EMBODIMENT In the drawings:

FIG. 1 is a perspective view of a lift truck of a kind to which thepresent invention is particularly adaptable and including clamp means towhich the hydraulic lines and control means of the invention areapplied;

FIG. 2 is a diagram of the hydraulic circuit of the invention and adiagrammatic representation of the clamp means;

FIG. 3 is a fragmentary schematic view representing certain maincomponents of the lift truck and the arrangement therein of certainfluid lines;

FIG. 4 is a view similar to FIG. 3 but showing a different arrangementof the same fluid lines; I

FIG. 5 is a diagram of the hydraulic system showing certain elements inactive condition in a first step of an operation;

FIG. 6 is a diagram similar to FIG. 3 but showing other elements thereofin active condition;

FIG. 7 is a view similar to.FIGS. 3 and 4 but showing different elementsin active condition;

FIG. 8 is a view similar to FIGS. 3-5 but showing still differentelements in active condition;

FIG. 9 is a view similar to FIGS. 3-6 and showing additional elements inactive position; and

FIG. 10 is a view similar to FIGS. 3-7 with still other elements inactive position.

Referring in detail to the accompanying drawings, at-

tention is directed first to FIG. .1 which shows a lift truck in itsentirety at 10 which may be of the type disclosed in U. S. Pat. No.3,184,088, to Berge, assigned to the assignee of this invention. It willbe understood that the specific kind of lift truck, other than theparticular features described in this disclosure, may be as desired.Such a lift truck may includea vehicle 12 and a lifting component 14,the lift truck including a body 15 and a mast 16 on which the liftingcomponent 14 is mounted and which rides in vertical directions inlifting and lowering movements. The lifting component 14 in-' corporatesclamp means 18 which includes a pair of clamp arms 20 individuallyidentified as 20R and 20L (for right and left), which engage a load 23to be lifted or handled. The lifting component 14 includes a carriage 21directly mounted to the mast l6 and movable vertically thereon in theusual mannerby hydraulic means. The range'of vertical movementofthelifting component on the'mast is determined by the desired extent oflifting of the load, and whatever that height is, the fluidjlinesleading to the clamp means 18 must accommodat e it and to accommodatethe greatest and the least extension, either by the provision of slackin the fluid lines or reeling them out or in, according to the verticalmovements of the clamp means.

In such vertical movements of, the clamping component, the fluid lineswhich are disposed over the mast and lead to the clamping component, areworked to a very great extent, either by moving them to provide or takeup slack, or in moving them over sheaves, and this results in relativelyrapid deterioration of the lines. The greater the number of the lines,the greater will be the total deterioration, and the lesser the numberof lines of course the lesser will be that deterioration, and it isdirectly in connection with this phenomenon that the present inventionhas particular significance. The present invention includes an effectivenumber of fluid lines leading over the mast to the clamping means as lowas three, and in come cases it may be desirable to have four, both insharp contrast to the usual number, six, utilized heretofore for thesame kind of operation.

Mounted in the carriage 24 are piston-cylinder units or jacks 24, 25(see FIGS. 1 and 2) having cylinders 26, 27 and pistons 28, 29,respectively. The cylinders are fixedly mounted in the carriage againstdisplacement in all directions and particularly transversely, and thepistons thereof respectively engage the clamp arms 20. Upon extension ofthe pistons, the clamp arms are spread and upon contraction thereof theclamp arms are drawn together, respectively clamping or releasing,depending upon whether they engage the load at outside surfaces orinside surfaces. The particular manner in which the load is engaged isnot of the essence of the invention, this manner of engaging the loadbeing known heretofore.

Attention is directed next to FIG. 2 showing the hydraulic system foroperating the clamp means 18, the latter being also shown in thisfigure. The hydraulic mechanism includes a pump 30 drawing fluid from areservoir or sump 32 and pumping it through a common line 34 andbranches 35, '36, 37 leading to manually operated, oppositely actingcontrol valves 38, 39, 40. Returning from the valves, are branches 41,42, 43 of a common'return line 44 returning to the reservoir 32 and thepump.

Thecontrol valves 38, 39, 40 are of known kind having means for stoppingthe flow of fluid in a neutral position, or enabling flow of fluidtherethrough in op posite directions respectively in opposite positionsof the valves. Thesevalves-(FIG. 2) are shown in neutral position inwhich all flow of fluid ischecked, although in FIGS. -10, respectiveones of the valves arein dif-' ferent positions indicating flow of thefluid in corresponding directions, in respective ones of the steps ofthe control operations.

In addition to the lines referred to above, are the following fluidlines: a line 45 leads from the valve 38 to a cross line 46 which inturn connects with a line 47 leading from the valve 39, both connectingwith a line 48 which includes a pilot check valve 49 and leads to across line 50 communicating with the rod sides of the cylinder-pistonsor jacks 24, 25. I

Leading from the valve 38 is another line 52 communicating with a line54 which includes a first pilot check valve 56, a second pilot checkvalve 58 and a shuttle valve 60. The line 54 continues beyond the valve56 and communicates with the control valve 40. Also communicating withcontrol valve 40 is another line 62 communicating with the line 54. Thecontrol valve 39 has a line 64 also communicating with the line 54.

Leading from the line 54 outwardly beyond the check valve 56 is an outerline 66 leading to the base end of the jack 24. Additionally anotherouter line 68 leads from the lines 54, 62, at a point outwardly beyondthe check valve 58, to thebase end of the other jack 25. The line 54includes a portion 54a between the outer lines 66, 68 which may bereferred to as a by-pass line.

Additional lines in the circuit include a pilot line 70 leading from theline 45 to the check valve 56, and a pilot line 72 leading from the line47 to the check valve 58; an additional pilot line 74 leads from theshuttle valve 60 to the check valve 49.

The check valves 56 and 58 prevent opening of the check valve 49 whenside shiftingv the two clamp arms together. A pilot check valve 76 isplaced in a line 78 connected between the pilot line 74 and the line 48,and communicates with an element 32a of the reservoir 32 to relieve anypressure trapped between the shuttle valve 60 and the check valve 49.

The clamp means 18 is arranged for the arms thereof to be individuallymoved inwardly or outwardly, or together shifted to the-left or to theright. The clamp arms may be moved inwardly for gripping the load, andmoved outwardly for releasing the load. When the clamp arms are shiftedto the left or right, they are effective for shifting the load itself incorresponding directions. It is desired that the clamp arms beindividually moved in or out, and it is found not necessary that they bemoved inwardly or outwardly together in a single movement, althoughthese movements may be accomplished if it should be so desired byconjoint movements of the corresponding individual control valves. Thecontrol valve 39 is utilized for moving the clamp arm L individually,the control valve 38 for moving the clamp arm 20R individually, whilethe con trol valve 40 is utilized for shifting both together.

Assuming as a first step, it is desired to move the left clamp arm 20Linwardly by contracting the jack 25. To do so the control valve 39 isshifted to the position shown in FIG. 5 (to the left from FlG. 2)wherein the oil is forced from the pump 30 through the line 34 andbranch line 36; through the valve 39 and then out through the line 47.The oil under pressure from the line 47 then flows through the line 48,the check valve 49 and into the cross line 50 and the rod ends of thejacks. The pressure in the line 47, which is also developed in the line46, is transmitted through the pilot lines 70, 72 to the checkvalves 56,58, opening those valves. The oil in the base end of the jack 25 returnsthrough the line 68 and line 54, through the check valve 58 which isthenopen, and then the line 64 inv return to the control valve 39. Thecircuit is thus completed through the branch line 42 communicating withthe return line 44 to the reservoir 32 and the pump 30.

In this same step, the jack 24 is constrained against movement becausethe oil in the base end thereof is obstructed from returning; the returnwould be through the line 66, and in one direction (downwardly) throughthe line 54 (the check valve 56 being open) and line 52 but the latteris obstructed because the valve 38 is in neutral position; the otherpath of return of the oil from the base of the jack 24 is from the line66 through the line 54 (upwardly) and then to' the valve 40, but at thisend also it is closed. Hence only the jack 25 can be actuated.

To move the clamp arm 20L in the opposite direction, or outwardly, thevalve 39 is moved to the opposite position, shown in FIG. 6, and in suchposition the oil leaves the pump 30 through the line 34 and branch 36and then flows to the valve '39 and the line 64. The oil in line 64progresses through the line 54 the jack 25. The oil is relieved from therod end of this jack, and enabling the jack to be'extended, through thecross line 50 and then the line 48; the oil continues through the checkvalve 49 in reverse direction, this check valve being opened by thepressure through the pilot line 74 which is produced by the shuttlevalve being moved to its position shown in FIG. 6; the oil thencontinues in return direction through the line 47 and through the valve39 and then through the branch line 42 and return line 44 to thereservoir and the pump. At the same time the jack 24 is prevented frommoving the right clamp ann inwardly, because of the obstruction torelief of oil from the base end of that jack, the relief movementotherwise being through the line 66, line 54 which is closed at valve40, that valve being in its neutral position. The other path of thereturn of the oil from the jack 24 would be through line 66, then line54 (down) to check valve 56 which is closed, since no pressure has beendeveloped in the with FIGS. 5 and 6, whereby it will be seen that theclamp arm R is moved in the direction stated.

FIG. 8 is a correlative of FIG. 6 and shows the position of the controlvalve 38 for moving the right hand clamp arm 20R outwardly, and is anopposite situation relative to FIG. 7.

The arrangement is also adaptable to shifting the clamping meanstogether in either direction, i.e., while holding the load, shifting itto the left, or to the right. FIGS. 9 and 10 show the arrangement of thecircuit for accomplishing these movements, the control valve 40 beingused for this purpose, as stated above. To shift the clamp means to theright, for example, the valve 40 is shifted to the position representedin FIG. 9, i.e., to the right from its neutral position of FIG. 2; insuch position of the valve, the oil is pumped from the pump through theline 34 and branch line 37 and through the valve to the line 54, the oilthen going through the line 66 to the base end of the jack 24. Thepiston in that jack is forced to the right, and the oil is forced out ofthe rod end of that jack and into the rod end of the other jack and thusforcing the piston in the latter jack to the right. The oil returns fromthe base end of the jack 25 through the line 68 and line 62 through thevalve 40 and in return through the branch line 41 and line 44 to thereservoir 32 and pump 30. I

To shift the clamp means in the opposite direction, i.e., to the left,the valve 40 is shifted to the opposite position, relative to that ofFIG. 9, as represented in FIG. 10. The diagram of FIG. 10 shows thedirection of oil flow, and upon consideration thereof as compared withthe direction of flow in FIG. 9, the operation now referred to will beunderstood.

Summarizing the actions of the fluid lines and valve means, the checkvalves 56, 58, 49 are open 'when either of the control valves 38, 39 isactuated, and the shuttle valve 60 controls the flow from the actuatedcontrol valve through the corresponding check valve 56, 58; for examplewhen the control valve 39 is actuated to the position shown in FIG. 6,the shuttle valve is forced to upper position enabling flow throughcheck valves 58, 49, but preventing flow through the check valve 56;when the control valve 38 is actuated to the position shown in FIG. 8,the shuttle valve is forced to lower position enabling flow throughcheck valves 56, 49, but preventing flow through check valve 58; whenonly the control valve 40 is actuated, in either direction, all thecheck valves are closed, and the circuit is through that control valve,the outer lines and the jacks. In the operations represented in FIGS. 5,7, 9, 10 the shuttle valve does not enter into the control functions andit assumes a random position or the position it happens to be in at thattime.

The apparatus of the invention is effective in the utilization of threehydraulic lines namely 48, 66, 68, leading to the clamp means, theselines necessarily extending over the mast as represented in FIG. 1, andthese three lines will accomplish all of the necessary clamping andreleasing movements of the clamp means for clamping a load and moving itin the usual fashion. Thus these three lines take the place of six linesheretofore utilized and found necessary. Because of the fact that theline 48 extends over the mast, and is subjected to the movements andactions leading to deterioration of any line in such situation, it maybe desired that the check valve means 49 be mounted on the clamp meansitself, asindicated in FIG. 4, rather than on the vehicle body asrepresented in FIG. 3, because if the pressure line 48 should breakbecause of the deteriorating effect in running over the sheaves, thecheck valve would prevent dropping of the load, because of the smalllikelihood of breaking of the section of the line between the checkvalve and the jacks. In such case there would be four lines to theclamping means, namely 48, 66, 68 and the pilot line 74; however it maybe desired, and it is practical to do so, to put the check valve 49 onthe vehicle body, (FIG. 3), and in that case the pilot line-74 would notextend to the clamp means,

' and only the three lines 48, 66, 68 would do so, but in this case carewould have to be taken that the line 48 be replaced sufficiently oftento prevent its breaking.

As indicated above, both clamp arms 20 can be actuated simultaneously,by simultaneously actuating the control levers which move the valves 38,39, for gripping or releasing, although this would not be a normal orroutine operation.

I claim 1. A hydraulic lift truck comprising a hydraulic motor, a fluidline system, clamp means including laterally movable clamp arms, ahydraulic jack operatively connected with each clamp arm for'moving itlaterally, a common fluid line communicating with the jacks, an outerline communicating with each jack individually, three manual controlvalves each having a neutral position and including a first and a secondassociated individually with the jacks, and a third associated with bothjacks, the first controlvalve being operative for establishing a circuitthrough the common line and a first associated outer line and theassociated jack, the second control valve being operative forestablishing a circuit through the common line and a second associatedouter. line and the associated jack, a single check valve in the commonline, and a single check valve between eaeh outer line and therespective first and second control valve and a shuttle valve betweenthe check valves in the outer lines, all said check valves normallyblocking flow in direction toward the control valves, each of the firstand second control valves being operative for opening the check valvesand being operative for doing so upon establishing a circuit through theassociated jack, and the check valves being closed when the first andsecond valves are in neutral position whereby to shut off the threelines mentioned from the first and second control valves, and the thirdcontrol valve when actuated being operative for establishing a circuitthrough the outer lines and both jacks, said shuttle valve beingoperative for opening the check valve in the common line to enable flowof fluid through the common line to the actuated one of the first andsecond control which is being actuated valves.

2. A hydraulic lift truck according to claim 1 wherein the fluid linesinclude a by-pass line interconnecting the outer lines in by-passingrelation to the jacks, and said by-pass line includes the check valvesshutting off the outer lines from the first and second control valves.

3. A hydraulic lift truck according to claim 2 wherein the fluid linesinclude a pilot pressure line from each of the first and second controlvalves for opening the checkvalves in the by-pass line.

4. A hydraulic lift truck according to claim 3 wherein the lines leadingfrom the first and second control valves for opening the check valvesalso interconnect with the common line to the jacks.

5. A hydraulic lift truck according to claim 2 wherein the fluid linesinclude 'a line leading from each the first and second control valve tothe by-pass line and connected thereto at points between the checkvalves in the by-pass line and the check valves being arranged fornormally passing fluid from the associated control valves outwardly intothe corresponding outer lines.

6. A hydraulic lift truck according to claim 5 wherein

1. A hydraulic lift truck comprising a hydraulic motor, a fluid linesystem, clamp means including laterally movable clamp arms, a hydraulicjack operatively connected with each clamp arm for moving it laterally,a common fluid line communicating with the jacks, an outer linecommunicating with each jack individually, three manual control valveseach having a neutral position and including a first and a secondassociated individually with the jacks, and a third associated with bothjacks, the first control valve being operative for establishing acircuit through the common line and a first associated outer line andthe associated jack, the second control valve being operative forestablishing a circuit through the common line and a second associatedouter line and the associated jack, a single check valve in the commonline, and a single check valve between each outer line and therespective first and second control valve and a shuttle valve betweenthe check valves in the outer lines, all said check valves normallyblocking flow in direction toward the control valves, each of the firstand second control valves being operative for opening the check valvesand being operative for doing so upon establishing a circuit through theassociated jacK, and the check valves being closed when the first andsecond valves are in neutral position whereby to shut off the threelines mentioned from the first and second control valves, and the thirdcontrol valve when actuated being operative for establishing a circuitthrough the outer lines and both jacks, said shuttle valve beingoperative for opening the check valve in the common line to enable flowof fluid through the common line to the actuated one of the first andsecond control which is being actuated valves.
 2. A hydraulic lift truckaccording to claim 1 wherein the fluid lines include a by-pass lineinterconnecting the outer lines in by-passing relation to the jacks, andsaid by-pass line includes the check valves shutting off the outer linesfrom the first and second control valves.
 3. A hydraulic lift truckaccording to claim 2 wherein the fluid lines include a pilot pressureline from each of the first and second control valves for opening thecheck valves in the by-pass line.
 4. A hydraulic lift truck according toclaim 3 wherein the lines leading from the first and second controlvalves for opening the check valves also interconnect with the commonline to the jacks.
 5. A hydraulic lift truck according to claim 2wherein the fluid lines include a line leading from each the first andsecond control valve to the by-pass line and connected thereto at pointsbetween the check valves in the by-pass line and the check valves beingarranged for normally passing fluid from the associated control valvesoutwardly into the corresponding outer lines.
 6. A hydraulic lift truckaccording to claim 5 wherein said shuttle valve is in said by-pass line.7. A hydraulic lift truck according to claim 6 and wherein the checkvalve in the common line normally passes fluid from the control valvesto the jacks, and a pressure line interconnects the shuttle valve andcheck valve and is operative for opening check valve to reverse flow ineither of two opposed operative position of the shuttle valve wherebypressure developed by either of the first and second control valves isoperative for opening the latter check valve.